1. Field of the Invention
The present invention generally relates to hydroxycitric acid (HCA) and its salts, and more specifically to water soluble mixtures of calcium and potassium salts of HCA, and to methods of making the calcium and potassium salts and mixtures thereof. The invention also relates to the use of such compositions as nutraceuticals or dietary supplements.
2. Description of Related Art
The fruit acid hydroxycitric acid (HCA) is a naturally occurring fruit acid found in the rinds of the fruit of Garcinia cambogia, Garcinia indica and Garcinia mangostana. The identification of the acid, methods of isolation and analytical methods for estimating concentration were elucidated by Y. S. Lewis et al. in METHODS OF ENZYMOLOGY (Academic Press, N.Y. (1969)). Hydroxycitric acid has been investigated for its nutritional importance, and studies have shown that pharmacologic amounts of HCA can accelerate metabolism, leading to weight loss, improved glucose metabolism, can suppress the appetite, and can produce other physiological effects. Various researchers have evaluated HCA for its weight control properties, fat burning properties, lipid level lowering effect, appetite regulation, metabolic rate increase, and other effects. A number of U.S. patents have been granted based on the results of those studies and on various methods of extracting HCA from the Garcinia fruit. For example, U.S. Pat. No. 5,656,314 (Moffett et al.) describes a certain hydroxycitric acid concentrate and food products prepared therefrom. By that method, free hydroxycitric acid having a concentration ranging from 23 to 54% in aqueous media is obtained.
It has been found, however, that the free acid form of HCA is unstable, forming lactones which generally do not possess the desired bioactivity. Therefore, food preparations that incorporate the free acid in liquid form will not provide the full benefit of the functional product (i.e., HCA) in the final preparation. The liquid form of free HCA tends to be unstable during storage, so it may not be the optimal form for incorporation of HCA in food products.
In U.S. Pat. No. 5,783,603 (Majeed et al.) administration of potassium hydroxycitrate for the suppression of appetite and induction of weight loss is disclosed. This salt is prepared by treating Garcinia-extracted HCA with methanolic potassium hydroxide, and the potassium salt of HCA is dried under vacuum. In powder form, potassium hydroxycitrate is very hygroscopic in nature, and typically has very poor keeping qualities. Another drawback of this type of preparation is that the assay of HCA may be too low for some applications.
U.S. Pat. No. 6,160,172 (Balasubramaniam et al.) describes certain compositions containing soluble double metal salts of hydroxycitric acid. Group IA and IIA (i.e., Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba and Ra) salts of HCA are formed as powders after precipitating the Garcinia-extracted HCA solution with polar solvents. This process can contain solvent residues and high levels of chlorides in the final product, however. Potential contaminants such as chloride and oxalic acid limit application of the product where the original taste, color and fragrance of the base material, such as a food or beverage, cannot be compromised. Another drawback of a method such as this is that it can be quite cumbersome due to the number of steps.
U.S. Pat. No. 6,207,714 (Clouatre et al.) describes the use of commercially available pharmaceutical preparations of a calcium, magnesium, potassium or sodium salt of hydroxycitric acid for increasing a person's glucose metabolism.
U.S. Pat. No. 6,221,901 (Shrivastava et al.) describes a method of making a purified magnesium hydroxycitrate preparation, and discusses its use as a medicament for treating cardiovascular disease. No food supplementation or body weight effects were noted in rabbits that were fed the magnesium hydroxycitrate preparation.
It is well known that hydroxycitric acid is unstable in its free acid form, so it is typically prepared as its salt for stability and for use in any of the applications mentioned above. Some commercially available and commonly used salts include calcium salts of HCA standardized for 50%, 55% and 60% levels of HCA. The potassium salt form is also readily available as a 45%, 50%, 55% and 60% salt. One drawback of typical commercially available calcium HCA salt preparations is that they are not very soluble in water. This severely limits its applicability for use in drinking water, beverages, ice cream, candies and in food. Another disadvantage of most calcium salts of HCA that are available today is that they typically deliver only a maximum assay of 60%, thereby limiting the total availability of HCA in any composition.
The potassium salt of HCA overcomes the major disadvantage of the calcium salt (i.e., insolubility) due to the good water solubility of the potassium salt of HCA. However, due to the high level of potassium in the salt, the potassium salt leaves a strong pungent taste of potassium. This tends to interfere with the taste profile of the food, or beverage, which limits the amount of potassium hydroxycitrate that can be incorporated into a food to levels that are below the amount needed to achieve the desired functional effects of the HCA in the recipient. Another disadvantage often encountered with the potassium salt is a tendency to form lumps during storage due to its highly hygroscopic nature, thus reducing the shelf life of the HCA salt. Commercial manufacture is also made cumbersome due to the undesirable hygroscopic property. The assay of HCA in conventional potassium hydroxycitrate preparations is also typically low, at 60% or less.
PCT Published Patent Application No. WO 99/03464 (Raju) describes certain hydroxycitric acid compositions containing 40% or more HCA, 5-13% calcium and about 9-20% potassium or about 5-10% sodium for use as dietary supplements and food products to reduce body weight. Hydroxycitric acid lactone content is said to be less than approximately 4%. A synergistic relationship between the calcium content and the potassium (or sodium) content is described. An acetone refining step is employed in preparing the HCA extract. As previously mentioned, potentially toxic residues of chemicals employed during manufacture may be a concern in some HCA compositions intended for consumption.
There exists a need for a pure, stable, highly soluble formulation of HCA salts that addresses the above-identified problems and eminently lends itself for incorporation into consumables such as drinking water, beverages, nutraceuticals, power bars, ice cream, and the like. Such products are useful as diet aids to help with weight reduction. Also needed is a better and more commercially attractive way to prepare such HCA salt formulations.